A parallel optical communications module is a module having multiple transmit (TX) channels, multiple receive (RX) channels, or both. A parallel optical transceiver module is an optical communications module that has multiple TX channels and multiple RX channels in the TX and RX portions, respectively, of the transceiver. The TX portion comprises components for transmitting data in the form of modulated optical signals over multiple optical waveguides, which are typically optical fibers. The TX portion includes a laser driver circuit and a plurality of laser diodes. The laser driver circuit outputs electrical signals to the laser diodes to modulate them. When the laser diodes are modulated, they output optical signals that have power levels corresponding to logic 1s and logic 0s. An optics system of the transceiver module focuses the optical signals produced by the laser diodes into the ends of respective transmit optical fibers held within a connector that mates with the transceiver module.
The RX portion includes a plurality of receive photodiodes that receive incoming optical signals output from the ends of respective receive optical fibers held in the connector. The optics system of the transceiver module focuses the light that is output from the ends of the receive optical fibers onto the respective receive photodiodes. The receive photodiodes convert the incoming optical signals into electrical analog signals. An electrical detection circuit receives the electrical signals produced by the receive photodiodes and outputs corresponding amplified electrical signals, which are processed in the RX portion to recover the data.
There is an ever-increasing demand in the optical communications industry for optical communications systems that are capable of simultaneously transmitting and receiving ever-increasing amounts of data. To accomplish this, it is known to arrange multiple parallel optical transceiver modules in an array such that all of the modules simultaneously transmit and receive multiple optical data signals over multiple TX and RX channels. A variety of array configurations exist in the optical communications industry. For example, one known type of array configuration includes multiple multi-fiber connector modules known in the industry as MTP® connector modules. In the array, each MTP connector module plugs into a respective receptacle that is secured to a front panel of an optical communications system. This type of configuration is typically referred to as an edge-mounting configuration due to the fact that the modules plug into the front panel, and thus are connected on an edge of the optical communications system.
An alternative to edge-mounting configurations are mid-plane mounting configurations. A mid-plane mounting configuration is one in which multiple parallel optical transceiver modules are mounted in the plane of a motherboard printed circuit board (PCB). One known parallel optical transceiver module that is mid-plane mounted is the Snap 12 transceiver module. The Snap 12 transceiver module comprises a 12-channel TX module and a 12-channel RX module. Each module has an array of 100 input/output (I/O) module locating pins that plugs into a 100-module locating pin ball grid array (BGA), known as a Meg-array. The Meg-array is, in turn, secured to the host PCB motherboard.
Other mid-plane mounting solutions exist or have been proposed for mounting multiple parallel optical transceiver modules on a motherboard PCB. One of the problems associated with the existing or proposed mid-plane mounting solutions is that they limit the density with which the modules can be mounted on the motherboard PCB. Each module is typically mounted in a socket that has inner side walls that have flat edges that operate to position and align the modules. The sockets are typically either secured directly to the motherboard PCB or to a leadframe that is secured to the motherboard PCB. The sockets themselves consume space and therefore increase the pitch (i.e., the lateral spacing) between adjacent modules. In addition, the flat edges located on the inner side walls of the sockets also consume space and therefore also increase the pitch between adjacent modules. Both of these factors reduce the density with which the modules can be arrayed in a mid-plane mounting configuration.
A need exists for a method and an apparatus that increase mounting density and improve alignment of parallel optical transceiver modules in a mid-plane mounting configuration.